Pre-germination Treatments Research Articles

Effects of storage temperature and pre-treatments on seed germination of Primula mallophylla and P. sertulum (Primulaceae), two narrowly-distributed endemic species from southwest China

Primula mallophylla and P. sertulum are wild ornamental species of south-west China, but the responses of their seeds to storage have not been determined. When seeds were dry-stored for 24 months at room temperature (RT) (ca. 21°C) and at 4°C, germination increased during the first six months, but then decreased over the following 18 months. The decrease in germination was slower for seeds stored at 4°C than for those stored at RT. When seeds of these two species were dry-stored at -20°C for 24 months, germination percentage was significantly higher than that of the control seeds by the sixth month; the high germination percentages persisted at 24 months. In addition, pre-germination treatments (i.e., immersion in 100 μmol L -1 GA3 for 24 hours, cold stratification for 30 days or both) improved the final germination and reduced mean germination time of P. mallophylla seeds stored for 12 months at RT, but not those of P. sertulum. Taken together, storing seeds at -20°C is feasible and convenient for both primrose species; thus, it is possible to safely store seeds for future research and conservation.

Thermal optima for seed germination of 30 tree species from Central Amazonia: a comparison of approaches and a new proposal

This study compared the seed germination of 30 tree species from Central Amazonia using a wide temperature range (5-40°C with 12 hours of light daily). Seeds were submitted to pre-germination treatments, whenever necessary, sown on vermiculite or germitest paper, and normal seedling development was assessed until stabilisation. With the same data set, seeds' optimal germination temperature (Topt ) was determined by comparing the following approaches: (i) 2-step, the temperature with the highest germination and the shortest time to seed population reach 50% of germination was chosen; (ii) the highest Germination Speed Index (GSI); (iii) using the formula developed by Olff and collaborators (Olff's approach); (iv) three species were evaluated with Covell's approach; and (v) new formulas for Topt calculation are proposed, based on germination success and five different variables of germination rate (Cipriani's approach). Comparing the results, Topt differed between 0.6-10.0°C. GSI and 2-step indicated generally higher values than Olff's formula. The minimum and maximum Topt differences between Cipriani's approaches were between 0.1-2.2°C. Our study showed that Toptshould be determined for each species as, even the 30 Amazonian tree species of the same habitat, Topt ranged between 22.5 and 32.5°C.

Methods for overcoming dormancy in cassava seeds

The propagation of cassava via seminal is an option but faces problems due to dormancy and slow germination. Therefore, the objective was to evaluate the effect of pre-germination treatments, on overcoming Manihot esculenta seed dormancy, clone Gabriela, cultivated in Roraima, Brazil. The experiment was a completely randomized design, with four replicates of 25 seeds, each in seven treatments: intact seeds (CONTROL); lateral scarification the seed (LS); removal of the caruncle (RC); scarification of the caruncle (SC); immersion of the seeds in sulphuric acid for 10 minutes (SA10); for 20 minutes (SA20) and for 30 minutes (SA30). The seeds were sown in trays containing river sand, washed and passed through a 2 mm mesh sieve. The following variables were analyzed: seedling emergence (SE), average emergence time (MET), emergence speed index (ESI), percentage of firm seeds (PFS), percentage of hard seeds (PHS) and percentage of deteriorated seeds (PSDET). The LS (89±7%) and SC (82±5%) treatments were superior to the others, obtaining the shortest MET (11.7±0.38 and 12.8±0.69 days, respectively) and consequently the highest IVE (1.55±0.22 and 1.74±0.22). Sexual propagation of cassava is possible. Lateral scafifying the seeds until the inside of the tegument with exposure of the endosperm with the caruncle intact (LS) and Scarifying the of caruncle until the inside of the tegument (SC) were more efficient seedling emergence and in counting normal cassava seedlings. Soaking seeds in sulphuric acid (AS10; AS20 and AS30) does not overcome the dormancy of cassava seeds.

Seed Characterization and Evaluation of Pre-Germinative Barriers in the Genus Alstroemeria (Alstroemeriaceae)

The genus Alstroemeria originates from South America, and Chile is one of the countries showing the highest number of taxa (49), of which 40 are endemic. However, anthropogenic and environmental factors are affecting the survival of these species; therefore, the conservation of their genetic variability is of great importance, and can be achieved through seed propagation. Seeds of this genus normally show dormancy, which prevents their germination under favorable conditions. The objective of this work was to understand the pre-germinative barriers to develop a seed propagation protocol for native alstroemerias and to determine the best method to break their dormancy. Seeds from 10 Alstroemeria species native to Chile were collected from the Coquimbo Region to Maule Region, and 5 pre-germination treatments combining scarification and stratification methods were evaluated. Moreover, a morphological and biochemical evaluation of the seeds was performed. The results showed a positive and significant effect on the percentage of emergence using seed soaking in water and cold stratification at 13 °C, obtaining the best results in A. pelegrina and A. angustifolia subsp. angustifolia (98.33% and 91.67%, respectively) after 30 days. The morphological characterization of seeds showed a wide range of size (diameter), from 2.18 mm (A. pulchra subsp. pulchra) up to 3.43 mm (A. pelegrina), and different shapes (pseudospherical and angular) and textures (rough and smooth). The highest phenol and tannin concentrations were observed in A. hookeri subsp. maculata with values of 4.71 and 30.95 mg g−1 of seeds, respectively. A bigger size of the seed and a higher concentration of phenols could be related to a higher % of emergence of alstroemeria seeds.

Seed morphology and germination of Willd. ex Schult. emulating environmental conditions within ant nest.

Damiana (Turnera diffusa Willd. ex Schult.) is a species of plant used in traditional Mexican medicine for its aphrodisiac properties. Although it has a high commercial demand, both nationally and internationally, its sexual propagation is not usual due to the low percentage of seed germination. It has been proposed that ants play an important role in germination, due to the presence of elaiosomes. Therefore, the objectives of this study were to characterize the seed morphology of T. diffusa for agronomic purposes, analyze their viability, and evaluate their germination by simulating environmental conditions of an ant nest. For the morphological characterization, 30 seeds were selected and evaluated for the variables of color, size, and weight. Viability was evaluated with a tetrazolium test using two lots of seeds collected in 2016 and 2017, with different concentrations and three exposure times at 40°C. The germination of T. diffusa was evaluated under three pre-germination treatments and nine germination treatments. The results of the study showed that the seeds of T. diffusa have an average size of 0.725 mm long and 0.182 mm wide; the color of the seeds varies from brown to black when ripe and yellowish white when immature. There are no significant differences in the viability percentage (60%) for seeds collected in 2016 and 2017 (p = 0.20). On the other hand, there are significant differences between all the pre-germination and germination tests analyzed. Seeds of T. diffusa have the highest percentage of germination (36%) with the presence of elaiosome and 500 ppm of GA3. The germination interval of the seeds occurs over a period of six to 39 days. The application of GA3 in the germination of the seeds indicates that they present a physiological latency which was inhibited at concentrations of 500 and 300 ppm.

In vitro assay of neutral electrolyzed water against Fusarium oxysporum and its application as germination pretreatment on tomato (Lycopersicon esculentum), lettuce (Lactuca sativa L.) and cucumber (Cucumis sativus) seeds.

Seed germination is critical for seedling procedures, and new technologies are required to increase crop yields. Some substances are considered elicitors or stimulating agents because they promote seed germination as well as plant growth (like root and plumule length, and germination rate among others). Some of these, could be applied during plant growth, or in earlier phases before germination as seeds pretreatment. Neutral electrolyzed water (NEW) is a solution of oxidizing agents mainly studied for its antimicrobial power mainly applied to food pathogens, and in less reports to phytopathogens. The objective of this work is to evaluate the effect of NEW on germination and morphological parameters of tomato (Lycopersicon esculentum), cucumber (Cucumis sativus) and lettuce (Lactuca sativa L.) seeds as well as to evaluate the in vitro activity of NEW against F. oxysporum. Two experiments were carried out to determine the in vitro and in vivo effects of NEW in seed pretreatment and another in vitro experiment was also carried out to determine antifungal effect against F. oxysporum. NEW in vitro treatments at 50 mg/L decreased spore concentration greater than 4 log spores/mL. Germination parameters and morphological variables were analyzed after NEW pretreatments. For in vitro germination, NEW pretreatments up to 75 mg/L did not show effect on germination parameters however highest dose was slightly adverse (4 % against water control). For in vivo germination, NEW pretreatment of 100 mg/L had a stimulating effect on the germination rate in cucumber seeds (100 % FGP against 83 % FGP for water control). For tomato seeds germination neither stimulate nor adverse effect was observed (same percentage as water control). For lettuce seeds germination an inhibitory effect for 12 and 24 h of exposure time was achieved (73 % NEW treatment against 90 % of water control). For tomato and lettuce seeds, the NEW pretreatment of 50 mg/L during 12 h increased its germination capacity.

Maturation indexes and physiological quality of seeds and fruits of Morinda citrifolia L.

The seeds of Morinda citrifolia L. present unevenness and delay in germination in relation to other fruit trees. Knowledge about the physiological quality of seeds is extremely relevant for the production of seedlings and propagation of the species. Thus, the objective was to study maturation indices and the physiological quality of seeds and fruits of M. citrifolia. Seeds from freshly picked fruits, fruits harvested after seven days of maturation and freshly dropped fruits were used. The extracted and processed seeds were submitted to the following pre-germination treatments: GA3, KNO3 and H2O. The following were analyzed: fruit length and diameter, seed length, width and thickness, number of seeds per fruit, average number of seeds per kg, weight of 1000 seeds, germination, germination speed index, shoot and root length, seedling dry mass and percentage of normal seedlings. The experimental design used was completely randomized, with three stages of fruit maturation and six treatments, with four replications of 25 seeds. M. citrifolia seeds do not show tegumentary dormancy. The seeds of freshly harvested fruits and fruits harvested after seven days of maturation do not need pre-germination treatments. GA3 promotes greater germination in seeds of fruits harvested from the ground. Fruits that have just fallen to the ground have a higher content of soluble solids and a higher content of acidity. The storage of fruit in a refrigerator for a week provides the maintenance of texture characteristics, such as hardness, adhesiveness, elasticity and gumminess. Fruits with greater hardness have higher physiological seed quality.

Magnetopriming enhance germination and seedling growth parameters of onion and lettuce seeds

The main objective of this study was to improve seed quality by using magnetic field (MF) as a priming method to increase germination percentages (GP) and seedling emergence percentages (SEP) in onion and lettuce seeds. MF treatments on pre-hydrated seeds, significantly increased GP (up to 80% for onion, 87% for lettuce) and SEP (up to 76% for onion, 86% for lettuce) in both species. Magnetic treatments in other saying magnetopriming helped to increase germination and seedling emergence speed in treated seeds as well. The shortening of mean germination time allowed the treatments to establish uniform and well-developed seedlings. Our findings indicate that magnetopriming could be used as a pre-germination treatment before sowing.

Sexual propagation of Abies religiosa (Kunth) Cham, by immersion in water at different temperatures and periods

Objective: To increase the germination percentage of Abies religiosa by immersion in water with different temperatures and periods.Design/Methodology/Approach: A completely randomized factorial experiment was carried out with five temperatures (10, Room temperature (Rt), 30, 40, and 50°C) and 13 periods expressed in seconds (10, 20, 40, 60, 600, 1200, 1800, 2400, 3000, 3600, 7200, 14400, and 21600), with a total of 65 treatments and 30 repetitions per treatment. The seeds were dipped in water with the temperatures and periods of each treatment to obtain the highest germination percentage.Results: The best pre-germination treatment (73% germination) was obtained with the combination of 40 °C and 7,200 s. Meanwhile, the treatments with the lowest percentage (14%) were the combinations 10 °C × 20 s and 10 °C × 40 s. Twenty-six treatments recorded a >50% germination, reaching a peak value of 8.56 at 11.7days. Study Limitations/Implications: Keeping the water temperature and theimmersion period constant during the experiment was more difficult in the longer treatments, with the lowest and highest temperatures.Findings/Conclusions: Abies religiosa registers acceptable germination percentages with the highest temperature (50 °C).

Fruit and Seed Morphometry and in Vitro Germination of Hollyhock Seeds

Alcea rosea L. is an ornamental shrubs that has many possible uses, including medical purposes. This species is mainly propagated by seeds, however, there are few studies that describe their morphometric characteristics, in addition, previous reports show that they have dormancy that makes the germination difficult. Therefore, this work aimed to determine the morphological characteristics of the fruit and seeds of A. rosea and to evaluate its in vitro seeds germination under different pregerminative methods in different culture media. For the morphological description, 25 fruits or seeds were evaluated. For the in vitro germination in the MS and WPM culture media, the pregerminative treatments were: T1 - untreated seeds (control); T2 - mechanical scarification (cut in the seed coat); T3 - thermal scarification (immersion of the seeds in water at 60 ºC for 16 min). The experimental design was completely randomized, in a 3x2 factorial scheme (pregerminative treatments x culture media), with eight replications and twenty seeds per replication. A visual scale was proposed to classify the seedlings vigor. The schizocarp hollyhock fruit is flattened and its diameter is greater than its height, and each fruit contains 33 seeds, on average. The seeds have approximately 4.2 mm in length and 100 seeds weight, on average, 0.89 g. The culture medium does not influence the seeds germination and the pregerminative treatments are not necessary for the germination. However, the mechanical scarification promoted the best germination speed index and the production of more vigorous plants.

Morpho-physiological studies on in vitro germination of Berberis empetrifolia Lam. (Berberidaceae)

Berberis empetrifolia is an endemic species from Chile that produces some bioactive compounds, highlighting the alkaloid berberine, which demonstrated antitumor properties. Taking into account the constant plant supply demand required for medicinal use, the establishment of in vitro propagation protocols allows plant multiplication, without affecting natural populations. Moreover, the in vitro germination is an efficient strategy to obtain axenic plants. The aim of this study was to establish the in vitro germination and to characterize seeds morphology and seedling development of B. empetrifolia. After decontamination of seeds, pre-germinative treatments were applied. Seed viability ranged from 75-90% and the embedding curve revealed permeable integument. The germination was characterized as epigeal phanerocotylar type. Seeds not submitted to pre-germinative treatments reached 10-30% germination rate (GR) and showed asynchronous germination. The most efficient pre-germinative treatment was the storage of seeds at 3˚C for 12 days followed by overnight soaking in GA3 solution associated to seed coat removal. This treatment allowed the seed dormancy to be overcome, reaching GR above 95% and resulting in synchronous germination. The in vitro germination protocol established for B.empetrifolia was efficient to produce phenotypically normal axenic seedlings, allowing their use as source of plant material for biotechnological, phytochemical and pharmacological studies.

Biometric characterization, post-seminal development and overcoming seed dormancy of Albizia polycephala (Benth.) Killip ex Record

Albizia polycephala (Benth) Killip, popularly known as angico-branco, belongs to the Fabaceae - Mimosoideae family, is a pioneer species used for environmental restoration, ornamentation and urban afforestation. Biometric characterization is an important tool to provide information on the type of germination, in addition to describing the morphology of the seed, it stimulates studies inherent to taxonomy, ecology and seed technology. For the production of seedlings, the most used form of propagation of this species is through seeds. Therefore, with the establishment of protocols to overcome dormancy of forest species, the producer will be able to choose the most efficient method and also the one that best adapts to his reality, both commercial and technological, providing an increase in the number of species destined to compose the models for the recovery of degraded areas to be implemented. Based on this, the objective of this work was to carry out the biometric characterization of the seeds, describe the post-seminal stages and verify the best way to promote the germination of A. polycephala using pre-germination treatments to overcome dormancy. The work was carried out at the Laboratory of Phytotechnics of the Campus of Engineering and Agricultural Sciences (CECA) of the Federal University of Alagoas (UFAL). The differentiation and development of A. polycephala seedlings was measured. In the dormancy breaking trial, the following treatments were used: i) control (intact seeds); (ii) chemical scarification by immersing the seeds in sulfuric acid for 5 min, followed by washing in running water; iii) cut (cut) on the side opposite the micropyle; iv) immersion in hot water (80°C) and cooling for 24 h; v) immersion in distilled water (room temperature) for 24 h; and vi) immersion in distilled water (room temperature) for 48 h. The seeds were incubated in a germination chamber at a constant temperature of 30°C. The design used was completely randomized, with 4 replications of 25 seeds per treatment, and the means were compared by Tukey's test at 5% probability. At the time of installation of the experiment, the seeds had a water content of 12.4%, with an average of 10.3 mm in length, 7.42 mm in width and 2.46 mm in thickness. Germination is epigeous and seedlings are phanerocotyledon. The physical rupture of the seed coat from the bud treatment contributed to the increase in permeability to water and gases, thus benefiting the germination process. Thus, topping can be recommended to overcome A. polycephala seed dormancy.

Effect of pre-germination treatments on seed germination of Passiflora setacea DC (Passifloraceae)


 setacea seeds without aril, were submitted to pre-germination treatments: T1(control); T2 (pre-soaking in Promalin® solution [gibberellin (GA4+7) + N-(phenylmethyl)-1H-purine 6-amine (6-benzyladenine) both at a concentration of 18.8 g.L-1] in bainMarie, 45 °C/20 min.; T3 (osmopriming with KNO3 at a concentration of 2.6g.L-1 H2O, 25 °C/1 day, with aeration); T4 (osmopriming with KNO3 at a concentration of 2.6g.L- 1 H2O, 25 °C/2 days, with aeration); T5 (T3 followed by T2) and T6 (T4 followed by T2). The initial moisture contents, ranging from 6.7% to 8% did not differ from each other (α 0.05). The highest fresh mass increment at 168h and the highest moisture content at the end of the germination test were achieved by T2, 40.9% and 44.3%, respectively. The lowest fresh mass increment at 168h was T1 (13.1%). Osmopriming with KNO3 and aeration contributed to better water absorption in T3 and T4 than in T1, but did not stimulate the germination performance of the seeds. The highest germination percentages and germination speed indexes were obtained from T2 seeds (92% and 8, 4595), T5 (96% and 11.7438) and T6 (94% and 11.6728) as well as the lowest mean germination times T2 (11.73 days), T5 (9.49 days) and T6 (8 .81 days), which did not differ statistically from each other (α 0.05). However, the germination process took less time for T2 seeds, 21 days. The combination of aryl removal and phytohormone solution in a bain-marie at 45 °C/20min. with or without osmopriming with KNO3 stimulated the germination process of P. setacea seeds.

Seed germination and sprouts production of Moringa oleifera: A potential functional food?

Moringa oleifera is a plant valued for its properties and applications in Ethnomedicine. It is cultivated in India, tropical Africa, and America; some regions use their different tissues as food supplements. Although germination can increase seedlings' phytochemical content, few studies have described the phytochemical content of moringa seedlings during early growth. This study aimed to investigate and discuss the limited information dealing with moringa seed germination, sprout production, and seedlings' chemical composition. This bibliographical research was systematically and thoroughly conducted using some of the most internationally-recognized databases. M. oleifera plants are characterized by their ability to grow under adverse environmental conditions. Although they generally germinate at rates greater than 70%, this response depends on the altitude, light periods, temperature, and nutrient availability. Pre-germination treatments have also been reported to help improve germination yields; the most common is soaking exposure. The production of M. oleifera sprouts is a viable option for obtaining functional food as this process can increase the content of nutrients (e.g. lipids, proteins) and phytochemicals (glucosinolates and phenolic compounds). Also, sprouts can be used as additives to enrich conventional foods. It is concluded that there is little scientific information describing the germination process and the chemical composition of both moringa seeds and moringa sprouts. Therefore, it is a niche opportunity to build new research that helps fill the informational gaps mentioned above. Meanwhile, it is envisioned that biotic or abiotic agents might modulate the germination process and their chemical compounds.

Effect of Pre-Germinative Treatments on Eight Priority Native Species for Reforestation in the Tropical Deciduous Forest

Increasing the germination percentages from chemical and/or mechanical processes in native species is vital for the conservation of the species. The objective was to evaluate the effect of different treatments on the germination process of species belonging to the tropical deciduous forest (TDF) in a forest nursery. Eight species of trees and shrubs reported to be native to the TDF were selected; the seeds were collected from various sites of the state of Queretaro, Mexico. A randomized design of four replicates with 25 seeds was used, for which three pre-germinative scarification treatments were evaluated for each species: (1) thermal scarification (TS), (2) mechanical scarification (MS), and (3) chemical scarification (CS). Germination was considered as the protrusion of cotyledons onto the substrate and was recorded every 48 h for 60 days. A significant difference was observed between treatments (p ≤ 0.05). The mechanical treatment (MS) obtained the highest germination percentage and the least variation, in contrast to the thermal, chemical, and control treatments, which presented the lowest amount of germinated seeds. The MS treatment was the most effective for all the species studied because it allowed for 100% of the germination to be achieved.

Effect of Dry Storage on Seed Germination of <i>Ephedra monosperma</i> (Ephedraceae)

Abstract—Effects of dry storage under ambient laboratory conditions on germination and survival was tested for seeds of rare species Ephedra monosperma. The seeds without pregermination treatment were placed in Petri dishes with a moistened filter paper at room temperature 20 ± 3 °C. Seeds maintain high germination when dry stored for 5 years (mesobiotic), further storage leads to a sharp decrease in germination. At the same time, dry storage of seeds does not change the time of the beginning of germination, the duration of germination and the curve of seed germination. Freshly harvested seeds and seeds stored at room temperature germinate 2–4 days after seeding, 50% of seeds – in 7 days, and 98–100% – within 2 weeks. The seed germination curve has two peaks; the highest one is the first, which is observed on the 3rd day from the start of germination.

Aqueous extract of coconut shell biochar as a pre-germination treatment increases seed germination and early seedling growth in chiltepín pepper (Capsicum annuum var. glabriusculum)

Since the fruit of the Capsicum annuum L. var. glabriusculum (Dunal) Heiser and Pickergil (chiltepín pepper) has a low germination rate, we sought to determine whether using an aqueous biochar extract could improve this. Germination tests were performed out in Petri dishes, using wild chiltepín pepper seeds collected in Sonora, México, which were exposed for 24 h to aqueous extracts of coconut shell biochar (CSBA) at different doses (0.05, 0.10, 0.25, 0.50, 0.75, and 1.00%, w/v) and a control comprising deionized water. In addition to quantifying the germination rate, we determined the physical quality, viability, imbibition, electrical conductivity, seed pH, and capsaicin content. The fast green test showed an ideal physical quality (p = 0.5475), an imbibition rate > 65% (p > 0.05), and high viability 98.4% (p > 0.05). The wild chiltepín pepper seeds exposed to the CSBA0.05 and CSBA0.25 treatments increased the percentage germination rate (p < 0.001) to 80.9% and 71.7%, respectively. A higher percentage of normal seedlings resulted from CSBA0.05, CSBA0.10 and CSBA1.00 (p < 0.01), and a greater shoot length was obtained with CSBA0.05 (p < 0.01). The exposure of wild chiltepín seeds to aqueous CSBA for 24 h at low doses (CSBA0.05 and CSBA0.25) increase the germination rate, while CSBA0.05 could enhance early seedling growth.

Influence of priming treatments on seed germination and growth characteristics of Moringa oleifera seedlings under laboratory and greenhouse conditions

Seed priming is the treatment of seeds with various priming substances to improve germination and seedling quality, and plant growth. The procedure entails advancing the seed to an equivalent stage of the germination process to achieve rapid and uniform emergence when planted, which is required in the case of Moringa oleifera to reduce the damage of ageing seeds, stimulate their performance, and overcome uneven germination rate due to seedcoat hardening, that leads to wide variation in terms of commercial qualities in the planting field. Therefore, a series of seed priming experiments were conducted to determine the optimal methods of priming treatments that maximise Moringa oleifera total germination, germination rate, and seedling vigour. Moringa oleifera seeds were treated with hydropriming, osmopriming (KNO3), and nutripriming (SeedActivator) for 4, 8, and 12 hrs. Germinability was improved by priming treatments. Results indicated that the highest germination percentage was recorded on seeds subjected to hydropriming (63.25%), followed by nutripriming (61.75%) and osmopriming (60%) with the exact duration of 4 hrs soaking time. All pre-germination treatments have significantly early mean germination days (MGT) compared to the unprimed seeds. In the seed pouch study, seeds treated with hydropriming for 4 hrs had shown the best results to improve roots growth in total root length (cm), root volume (cm3 ), the number of forks, and the number of crossings with 240.52 cm vs. 163.64 cm, 0.47 cm3 vs. 0.29 cm3 , 517.80 vs. 271.47 and 59.20 vs. 28.53 respectively when compared to unprimed seeds. The positive effect of priming can also be seen in the seedling growth of M. oleifera grown in a pot with two different growing media.

Functional seed traits as predictors of germination and seedling growth for species with potential for restoration in Caquetá, Colombia

Key messagePre-germination requirements are not accurately predicted by seed traits of size and mass. However, small-seeded species show high germination and slow early seedling growth rates.Deforestation in the tropics is one of the greatest biodiversity crises of the Anthropocene. In response, tropical countries such as Colombia have committed to restoring degraded lands and reconnecting forest fragments. To contribute to this mission, we evaluated how easy-to-measure seed functional traits predicted germination requirements and early seedling growth rates (RGRs) for 11 tree species native to the Andean-Amazon piedmont region. Pre-sowing treatments followed a 3 × 3 factorial design: three light conditions (full, partial, and no light) and three pre-germination treatments (hot water, abrasion, and control). A cluster analysis grouped species into three groups driven chiefly by highly correlated variables of seed size and mass. However, species within and among functional groups differed in their response to pre-germination treatments. One exception includes the small-seeded species group responding with little-to-no germination to the absence of light. Since functional traits were highly correlated, we used Principal Component Regression (PCR) to predict germination metrics (germination percentage, velocity, and vigor) and RGRs. The multivariate trait axis of seed size and seed mass measurements (PC1) correlated negatively with germination metrics and positively with RGRs. Our results highlight the challenges associated with using easy-to-measure functional traits to deduce the most effective pre-sowing treatment. Other more relevant functional traits can be measured in lab, but a shotgun approach to testing pre-germination treatments may be more cost-effective. High germination in small-sized seed species highlights the early-successional niche these species occupy, but reduced RGR may represent a tradeoff associated with having relatively few resources stored in seed.

Tratamentos pré-germinativos em sementes de pitaya (Hylocereus spp.) para atenuação do estresse hídrico

ABSTRACT The use of mitigating agents to minimize the deleterious effects of water stress is a promising alternative for plant species, especially during germination and initial seedling development. Thus, the objective was to evaluate the effect of different pre-germination treatments as mitigating agents of water stress during germination and initial development of pitaya seedlings of the species Hylocereus undatus and H. costaricensis. The experiment was carried out in a completely randomized design, in a 2 x 6 factorial scheme, corresponding to two pitaya species and six pre-germination treatments (T1 = 0.0 MPa (control), T2 = -0.2 MPa (water stress); T3 = hydropriming + water stress; T4 = gibberellic acid + water stress; T5 = salicylic acid + water stress and T6 = thiamethoxan + water stress) with four replicates of 50 seeds. The variables analyzed were germination, germination speed index, shoot and primary root lengths, total dry mass, total soluble sugars and total free amino acids. The water potential of -0.2 MPa is limiting for germination and initial growth of H. costaricensis and H. undatus, with H. undatus being more tolerant to water stress in the germination phase. Pre-germination treatments with hydropriming, gibberellic acid, salicylic acid and thiamethoxan improve the physiological performance of H. costaricensis seeds, with gibberellic acid being the best attenuator of water stress. Gibberellic acid improves the physiological performance of H. undatus seeds under water deficit conditions.